According to the study published in the American Journal of Respiratory and Critical Care Medicine, a significant percentage of COVID-19 patients were suffering from interstitial lung disease after getting discharged. Interstitial lung disease is characterized by lung scarring, including idiopathic lung fibrosis. The scarring caused by this disease can make it difficult to breathe and get oxygen into the bloodstream, which can be irreversible and get worse over time.

The clinical trial conducted by the American Thoracic Society was taken up and compared to determine the exact percentage of patients who had this disease. The authors of the study examined the abnormal lung patterns on follow-up CT scans of COVID-19 patients discharged from the hospital. In the study, the CT scans of almost 3,500 people were compared to determine the risk of having residual lung abnormalities.

The findings of the study showed that around 11% of the hospitalized COVID patients had fibrotic patterning after recovery from the acute illness. The authors noted that many patients complained of prolonged breathlessness, which can be associated with fibrotic abnormalities in their lungs. 

(Source: https://theprint.in/health/hospitalization-during-covid-19-damages-lungs-study/1246020/ )